A gaming machine represented by a slot machine is highly popular among casino customers as a device that provides gambling that is easy to enjoy, and recent statistics also report that sales from gaming machines account for the majority of casino earnings. Initial slot machines were simple devices, wherein an inserted coin is received, a configured reel rotates and stops mechanically according to a handle operation, and win or lose is determined by a combination of symbols stopped on a single pay line. However, recent gaming machines, such as mechanical slot machines driven by a highly accurate physical reel via a computer controlled stepping motor, video slot machines that display a virtual reel on a display connected to a computer, and various gaming machines that apply similar technology to other casino games are quickly advancing. For the manufacturers that develop these gaming machines, an important theme is to provide an attractive game that strongly attracts casino customers as players, and improves the functionality of the gaming machine.
In consideration of this type of background, a symbol replacement process is proposed for recent gaming machines to provide change in the staging until the final game result is displayed by, after a symbol sequence is formed by temporarily stopping a reel, replacing a portion of the symbols configuring a symbol sequence with different symbols (for example, see Patent Document 1 described below). According to the symbol replacement process, even after a reel stops, a player can continue expecting to win, and interest in the game results by a player can continue for long time.